The dispersion characteristics of airborne pollen in the Shijiazhuang (China) urban area and its relationship with meteorological factors

In this study, a Tauber pollen trap was used in the urban area of Shijiazhuang to monitor continuously the outdoor air pollen from 2007 to 2011. The trap was emptied at regular intervals (typically 15 days). The results show that airborne pollen assemblages are generally similar each year among 2007–2011 and are responsive to the flowering times of plants, being dominated by pollen from woody plants in the spring and by pollen from herbaceous plants in summer and autumn. Two peak pollen influx periods, especially for the main allergenic pollen taxa, are seen, one between early March to early June and a second between late August to early October. During the four seasons, the main pollen taxa are Juglans, Artemisia, Platanus, Populus, Chenopodiaceae, Urtica + Humulus, Rosaceae, Pinus, Poaceae, Cereals, Quercus, and Betula, and all taxa other than Rosaceae were confirmed by relevant studies to be allergenic pollen taxa. RDA analysis of pollen influx and meteorological factors shows that in spring, temperature and humidity have significant effects on the pollen influx of woody plants; in summer, humidity and precipitation have significant negative effects on pollen influx of herbaceous plants; in autumn, temperature, water vapor pressure, and precipitation have a significant positive influence on herbaceous pollen influx; in winter, there were no significant correlations between airborne pollen influx and meteorological factors. The results reveal the dispersion patterns of airborne pollen and provide an important reference to appropriate construction of urban green systems and the reliable reduction in regional pollinosis.     

First aerobiological study in Mediterranean part of Croatia (Dalmatia): pollen spectrum and seasonal dynamics in the air of Split

The aim of this study was to investigate aerobiological dynamics of pollen in the Mediterranean part of Croatia in the air of the city of Split. Pollen monitoring during the period from 2005 to 2013 was performed using a Hirst volumetric trap. Among the identified pollen of 50 taxa, 21 were allergenic. The average annual pollen index was 33,513. Three pollination seasons were established: early winter season dominated by tree pollen, spring–summer season dominated by herbaceous plants and summer–autumn season with lower amounts of Parietaria and Cupressaceae pollen. According to the abundance, the main taxa were: Cupressaceae, Parietaria/Urtica, Pinus, Quercus, Olea, Carpinus/Ostrya, Poaceae, Platanus and Ambrosia. The annual pollen index together with the daily maximum concentrations showed an upward trend for selected taxa during the study period. The highest monthly pollen index and the highest biodiversity were recorded in April and the lowest during the late autumn and winter months. The pollen calendar created for the city of Split confirmed Mediterranean features of the pollen spectrum. The longest pollen seasons were recorded for Cupressaceae, Parietaria/Urtica and Poaceae pollen types. The correlations between pollen concentrations and meteorological parameters were analyzed. The correlations between pollen concentrations and temperature were positive, while the humidity and the precipitation mostly showed negative influence.     

A molecular phylogeny of the Old World cypresses (<Emphasis Type="Italic">Cupressus</Emphasis>: Cupressaceae): evidence from nuclear and chloroplast DNA sequences

Studies of phylogenetic relationships among cypresses of the Old World (Cupressus; Cupressaceae) have been plagued by unresolved relationships, poor branch support, and conflict between data sets and methods of analysis. In this study, we combined 5.4 kb of aligned DNA sequence and 157 binary characters with previously published data in examining phylogenetic relationships among Cupressus species. Bayesian and parsimony analysis of the combined data or of the nuclear data alone always recovered three principal clades of Cupressus; however, tests of phylogenetic incongruence could not distinguish between competing relationships among the three principal Cupressus lineages. In contrast, incongruence tests often found statistically significant conflict between the nuclear and plastid data, particularly with respect to the placement of C. chengiana. Consistent with previous studies and prevailing taxonomic opinion, we find C. darjeelingensis more closely related to cypresses of the New World (Hesperocyparis). In contrast, we placed accessions of C. assamica and C. tonkinensis, two putatively Old World species suggested to be misidentified New World taxa by some authors, within well-supported Old World clades. Statistical analysis of genetic distances suggests instances in which taxa recognized as distinct species by some authors are identical or nearly so and may best be considered a single taxon. Conversely, we identify instances in which infraspecific taxa are more distantly related to one another than those traditionally recognized as distinct species. Factors confounding cypress taxonomies, including poor morphological differentiation, misidentification, and the use of accessions of questionable provenance, are discussed.     

Dead Sea medical tourism: an allergological point of view

A 1-year study was conducted, with the aim to investigate the airborne allergens around the Dead Sea (DS), identify and quantify airborne pollen and spores in the DS region, and determine the different sensitization prevalence among various population groups to these aeroallergens. According to results, we also aimed to define “safe seasons” when there are no or only few aeroallergens in the atmosphere that surrounds the Dead Sea. A Rotorod and a Hirst trap were used for continuous monitoring of pollen and spores which were then identified. Sensitization to aeroallergens was assessed by skin prick tests (SPT) in three groups of allergic residents: foreign tourists, Israeli tourists, and local workers from the hotel industry. Air around the DS is by no means free of aeroallergens, 50 pollen and 43 mold types were identified. Pollen was from native plants, imported ornamentals, and others transported by winds from long distances. Overall pollen concentrations were lower around the Dead Sea than in the Tel Aviv region, but in certain months, they were higher around the DS. Marked seasonal variations in pollen and spore dispersal were observed. By SPT, hypersensitivity to Chenopodiaceae, Amaranthaceae, Cupressus, Solidago, Poaceae, Olea, Artemisia as well as molds such as Alternaria and Aspergillus, was found. As assessed by SPT, some of tourists and permanent residents are allergic to pollen, molds, and house dust mites. The presented study enables one to denote “safe” seasons when the concentration of airborne allergens is below “allergenic risk”: June–August and November–February. These seasons are the most suitable for allergic medical tourists.     

Seasonal distribution of airborne pollen in Manila,Philippines, and the effect of meteorological factors to its daily concentrations

Pollen-related allergic diseases are a growing health problem. Thus, information on prevalence of airborne pollen may serve as guide for clinicians to accurately manage allergic diseases. In this study, an aeropalynological survey was conducted from November 2013 to October 2014 in Manila, Philippines, to determine the seasonal distribution of the most prevalent airborne pollen and correlate the influence of meteorological factors on their daily concentrations. A volumetric pollen trap was placed on a rooftop, 21 m above ground level. A total of 5677 pollen grains from 18 pollen types were identified, of which Urticaceae, Cannabaceae, Poaceae and Moraceae were the most prevalent. Other pollen types observed that represented 1 % of the total pollen concentration, in descending order, were Terminalia catappa, Myrtaceae, Muntingia calabura, Verbenaceae, Amaranthaceae, Cyperaceae, Caricaceae and Mimosa sp. Of the total airborne pollen, 87 % were obtained during the dry season (November–May). Pollen concentrations peaked (55 %) during the summer months (March–May), indicating a positive correlation (p < 0.01) between pollen concentration and temperature (maximum and mean). Alternatively, only 13 % of the pollen concentrations were obtained during the wet season (June–October). It was observed that pollen concentrations were negatively correlated (p < 0.01) with rainfall and humidity. As the pollen collection was done for one sampling year, only an approximation of the daily concentration of the pollen types was identified and correlated with meteorological factors. Further data collection is required to generate an accurate pollen calendar for use in allergy studies.     

The impact of Sharav weather conditions on airborne pollen in Jerusalem and Tel Aviv (Israel)

Pollen grains have been a major focus of research mostly in temperate regions due to their effects on human health, especially allergies and asthma. The current study investigates a subtropical region characterized by a Mediterranean climate where Sharav conditions are experienced during the spring and autumn. The aim of the current study was to investigate whether Sharav conditions impacted airborne pollen concentrations of allergenic Amaranthaceae, Poaceae, Morus, Pinus, and Quercus more than standard Warm days during the main pollen seasons in the years 2010–2014 in Tel Aviv and Jerusalem (Israel). Slight variation was observed between the main pollen seasons in Tel Aviv compared to Jerusalem resulting from differences in temperature and relative humidity percentages. Additionally, more Sharav conditions occurred in Jerusalem than in Tel Aviv during the study period. The highest pollen concentrations occurred during Sharav days for Amaranthaceae, Poaceae, and Pinus but not for Morus and Quercus. Therefore, individuals who are allergic to Amaranthaceae, Poaceae, and Pinus pollen, and exposed to high pollen concentrations during Sharav days, might suffer more allergy symptoms than on Warm days.     

Airborne pollen in the El-Hadjar town (Algeria NE)

The diversity of airborne pollen grains in El-Hadjar town (northeast Algeria) was measured for 1 year, from July 1, 2012 to June 30, 2013, by means of the gravimetric method using Durham apparatus. The total number of pollen grains/cm² was calculated from slides that were changed daily. This aerobiological study documented the air concentration of pollen from 50 taxa, where 28 belonged to arboreal and 22 to non-arboreal taxa. The percentage of pollen from arboreal and non-arboreal taxa was 56 and 44 %, respectively. From the list, the major collected taxa causing allergy in humans dominant in the Mediterranean area were Cupressaceae (14.86 %), Olea sp. (7.18 %), Casuarina sp. (6.44 %), and Fraxinus sp. (3.83 %) among arboreal plants, whereas for the non-arboreal plants Poaceae (23.20 %), Mercurialis sp. (12.58 %), Plantago sp. (1.69 %), Urticaceae (0.95 %), and Chenopodiaceae (0.85 %). The highest pollen counts occurred in the period from February to April. The pollen calendar for the region presented in this paper may be a useful tool for allergologists and botanical awareness.     

Flowering phenology and potential pollen emission of three <Emphasis Type="Italic">Artemisia</Emphasis> species in relation to airborne pollen data in Poznań (Western Poland)

Artemisia pollen is an important allergen in Europe. In Poznań (Western Poland), three Artemisia species, A. vulgaris, A. campestris and A. absinthium, are widely distributed. However, the contributions of these species to the total airborne pollen are unknown. The aim of the study was to determine the flowering phenology and pollen production of the three abovementioned species and to construct a model of potential Artemisia pollen emission in the study area. Phenological observations were conducted in 2012 at six sites in Poznań using a BBCH phenological scale. Pollen production was estimated by counting the pollen grains per flower and recalculating the totals per inflorescence, plant and population in the study area. Airborne pollen concentrations were obtained using a Hirst-type volumetric trap located in the study area. Artemisia vulgaris began to flower the earliest, followed by A. absinthium and then A. campestris. The flowering of A. vulgaris corresponded to the first peak in the airborne pollen level, and the flowering of A. campestris coincided with the second pollen peak. The highest amounts of pollen per single plant were produced by A. vulgaris and A. absinthium. A. campestris produced considerably less pollen, however, due to its common occurrence, it contributed markedly (30 %) to the summation of total of recorded pollen. A. vulgaris is the most important pollen source in Poznań, but the roles of two other Artemisia species cannot be ignored. In particular, A. campestris should be considered as an important pollen contributor and likely might be one of the main causes of allergic reactions during late summer.     

Modelling the pollen season start in <Emphasis Type="Italic">Corylus avellana</Emphasis> and <Emphasis Type="Italic">Alnus glutinosa</Emphasis>

Hazel (Corylus avellana L.) and black alder (Alnus glutinosa (L.) Gaertn.) are important sources of airborne pollen and represent an allergen threat during the flowering period. Researches on airborne pollen concentrations in both species are useful in allergology, as well as for fruit production for hazel. The aims of the present study were: (1) to investigate the relationships between environmental conditions and the airborne pollen concentration of hazel and black alder during the flowering period by correlation and multiple regression analysis and (2) to predict the pollen season start (PSS) by using a sequential model, in order to obtain a helpful tool in allergology and hazel cultivation. In this study, the applied method defines the pollen season as the period in which 90 % of the total season’s catch occurred, using a data set of 18 years (1996–2014). The relationships between daily meteorological parameters (temperature, humidity, rainfall and wind speed) during the 14-day period that precedes the PSS and the PSS of hazel and black alder (day of the year) were investigated. The results showed that mean temperature and the number of rainy days before the PSS are the main factors influencing PSS for both taxa. Moreover, the chilling and heat needed to break dormancy were estimated in order to predict the PSS of both species. Different years and different thresholds of temperature and chill days were used to calibrate and validate the model.     

Pollen season of European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) and temperature trends at two German monitoring sites over a more than 30-year period

Although beech (Fagus) pollen are often disregarded, they play an allergological role. This study focused on pollen season (PS) of European beech (Fagus sylvatica L.) and mean yearly temperatures (T) at two climatically different sites (lowlands vs. Alps) in Germany. Pollen sampling was conducted with 7-day recording volumetric spore traps between 1982 and 2014. Both PS parameters (start, peak, length, annual pollen index [PI]) and T were compared in two periods (1982–1991 and 1992–2014), and correlations between PS and T were analysed. At both sites, average PS occurred earlier in the second period. Statistically significant differences were proved at the alpine site in terms of start and peak of the season, and PI. On average, PS in the lowlands was shorter and occurred earlier than in the Alps. As is the case with a lot of temperate tree species, beeches show the masting phenomenon and PI differed greatly among the years. Mast years were much less frequent than non-mast years, and the differences between the pollen sums were significant. Average pollen counts at the alpine site were about three times higher than in the lowlands. At both sites, higher T was significantly correlated with an earlier start and peak of the season, and an increased PI. Trends of T over the years were significantly positive. Temperature increase as a part of climate change may contribute to an earlier occurrence of the flowering season of European beech and to higher airborne pollen concentrations.     

Spatial and temporal variations in airborne <Emphasis Type="Italic">Ambrosia</Emphasis> pollen in Europe

The European Commission Cooperation in Science and Technology (COST) Action FA1203 “SMARTER” aims to make recommendations for the sustainable management of Ambrosia across Europe and for monitoring its efficiency and cost-effectiveness. The goal of the present study is to provide a baseline for spatial and temporal variations in airborne Ambrosia pollen in Europe that can be used for the management and evaluation of this noxious plant. The study covers the full range of Ambrosia artemisiifolia L. distribution over Europe (39°N–60°N; 2°W–45°E). Airborne Ambrosia pollen data for the principal flowering period of Ambrosia (August–September) recorded during a 10-year period (2004–2013) were obtained from 242 monitoring sites. The mean sum of daily average airborne Ambrosia pollen and the number of days that Ambrosia pollen was recorded in the air were analysed. The mean and standard deviation (SD) were calculated regardless of the number of years included in the study period, while trends are based on those time series with 8 or more years of data. Trends were considered significant at p < 0.05. There were few significant trends in the magnitude and frequency of atmospheric Ambrosia pollen (only 8% for the mean sum of daily average Ambrosia pollen concentrations and 14% for the mean number of days Ambrosia pollen were recorded in the air). The direction of any trends varied locally and reflected changes in sources of the pollen, either in size or in distance from the monitoring station. Pollen monitoring is important for providing an early warning of the expansion of this invasive and noxious plant.     

Pollen diversity in the atmosphere of Havana,Cuba

With a view to obtaining fuller information on airborne pollen content in the city of Havana, pollen sampling was carried out using a volumetric capture method, for the first time in Cuba. The study was conducted during 2 years (2011 and 2015). An annual pollen integral of 3414 grains was registered during the first year of study, whereas 5120 grains were observed along the 2015. Monthly maximum concentrations were recorded during April, June and July with total values close to 800 pollen grains. Of the 45 pollen types identified, Cecropia (38% of the total pollen identified in both years), Poaceae (18%), Urera type (9%) and Casuarina (6%) were particularly abundant. Although the main pollen types differed in terms of intradiurnal distribution, the highest concentrations were in all cases recorded between 0900 and 1300 hours. Maximum temperature was the variable most influencing airborne pollen counts in the air, with the exception of Casuarina. This paper sought to establish a methodological basis for the further development of aerobiological research in Cuba, thus helping to enhance the prevention and diagnosis of pollen allergies in the affected island population.     

Airborne pollen and fungal spores in Garki,Abuja (North-Central Nigeria)

The ambient atmosphere is dominated with pollen and spores, which trigger allergic reactions and diseases and impact negatively on human health. A survey of pollen and fungal spores constituents of the atmosphere of Garki, Abuja (North-Central Nigeria) was carried out for 1 year (June 1, 2011–May 31, 2012). The aim of the study was to determine the prevalence and abundance of pollen and fungal spores in the atmosphere and their relationship with meteorological parameters. Airborne samples were trapped using modified Tauber-like pollen trap, and the recipient solutions were subjected to acetolysis. Results revealed the abundance of fungal spores, pollen, fern spores, algal cysts and diatoms in decreasing order of dominance. The atmosphere was qualitatively and quantitatively dominated by pollen during the period of late rainy/harmattan season than the rainy season. Numerous fungal spores were trapped throughout the sampling periods among which Alternaria spp., Fusarium spp., Cladosporium spp. and Curvularia spp. dominated. These fungi have been implicated in allergic diseases and are dermatophytic, causing diverse skin diseases. Other pathogenic fungi found in the studied aeroflora were Dreschlera spp., Helminthosporium spp., Torula spp., Pithomyces spp., Tetraploa spp., Nigrospora ssp., Spadicoides spp., Puccinia spp. and Erysiphe graminis. Total pollen and fungal spores counts do not show significant correlation with meteorological parameters.     

Pollen movement by the bat <Emphasis Type="Italic">Artibeus jamaicensis</Emphasis> (Chiroptera) in an agricultural landscape in the Yucatan Peninsula,Mexico

Artibeus jamaicensis is a medium-sized frugivorous microchiropteran bat that complements its diet with nectar and pollen during the dry season. We investigated which species of pollen are carried by A. jamaicensis in order to determine its potential role as a plant pollinator in the northern Yucatan Peninsula. We collected pollen from the fur of 192 individuals throughout the year from April 2004 to March 2005. We recorded pollen from nine plant species of eight families and found five unidentified pollen types, with the highest pollen species richness recorded in June. A. jamaicensis moved pollen of Erythrina standleyana and Mimosa bahamensis, which have not hitherto been reported as visited by this species. The most abundant pollen in the samples was found to be that of three tree species: Ceiba pentandra, C. aesculifolia and Lysiloma latisiliquum. Very few samples contained pollen in the rainy season, when the bats fed mainly on fruits. A. jamaicensis can fly several kilometres among foraging locations and dispersed large amounts of pollen from tree species growing near cenotes as well as those not present at cenotes but occurring in other forest fragments, highlighting its importance as a pollen vector among forest fragments in the largely deforested landscape of the Yucatan Peninsula, helping to reduce the negative effects of forest fragmentation. Ceiba appears to benefit from the role of A. jamaicensis as a pollen vector, and the species play an important ecological role in the Yucatán landscape, supplying shade, nectar and fruit for wildlife.     

Aeropalynological spectrum of Hatay,Turkey, the eastern coast of the Mediterranean Sea

An aeropalynological study during the years 2014–2015 was performed in Hatay, which is a unique sociocultural and phytogeographical area located on the border of Turkey and Syria on the eastern coast of the Mediterranean. The sampling was performed by a Hirst-type volumetric sampler (Lanzoni VPPS 2000), and pollen grains of 54 taxa were identified, of which 83.21% of the annual sum belonged to woody taxa. The highest pollen concentration was recorded in February, of which a large amount came from the Cupressaceae/Taxaceae families. The diversity of the pollen reflected the vegetation of the area and plantations of the city center, but pollen grains from Euro-Siberian elements specific to Mount Amanos could not be recorded. Pollen types found at more than 3% of the annual pollen index and considered dominant pollen types were as follows: Cupressaceae/Taxaceae (50.86%), Olea europaea (12.67%), Moraceae (7.20%), Poaceae (5.99%), Quercus (5.35%), Urticaceae (3.79%) and Pinus (3.70%); almost all dominant pollen types in the city atmosphere were previously stated to be allergic. The main pollen season starting dates of common pollen types found were one or two weeks earlier than those of the surroundings. Many statistically significant correlations were found between daily pollen concentrations and daily meteorological parameters, e.g., Cupressaceae/Taxaceae Poaceae and Urticaceae pollen correlated negatively with mean temperature in both years, and in the hindermost two families daily pollen amounts significantly correlated with wind speed in the second year. Daily Olea europaea pollen concentration showed a significant negative correlation with the amount of total daily rainfall in the second year.     

An aeropalynological survey in the city of Van,a high altitudinal region,East Anatolia-Turkey

Pollen concentrations in the atmosphere of Van city has been monitored for two consecutive years (2010–2011). This was the first detailed aeropalynological study for the elevated East Anatolia Region of Turkey. The sampling was performed by Hirst-type volumetric sampler, and pollen grains of 35 taxa were identified. The main pollen producers of the pollen flora were recorded as: Poaceae (20.94 %), Cupressaceae (10.53 %), Fraxinus (8.56 %), Chenopodiaceae/Amaranthaceae (7.77 %), Populus (7.75 %), Quercus (6.70 %), Platanus (6.68 %), Morus (5.57 %), Plantago (3.03 %). The pollen spectrum reflected the floristic diversity of the region, and the highest pollen concentration was recorded in April. There were a great percentage of allergenic taxa found in the city atmosphere, otherwise many of them scored under threshold values for risk of pollinosis. Statistical analyses were performed for correlating daily pollen concentrations of dominated pollen types concurrent with the data of meteorological parameters in MPS periods and number of significant correlations found. In addition, comparing 2-year data in terms of pollen concentrations and meteorological factors in MPS durations, many variables were found explanatory and concordant with the data. MPS starting dates of many plant taxa were found nearly a month later compared with western sites and lower altitudes of the country as well as Mediterranean countries; this case is mostly thought the ecological factors of the study area which directly affects the plant growth about the timing.     

Phylogenetic Analyses of Cretaceous Fossils Related to Chloranthaceae and their Evolutionary Implications

Chloranthaceae were one of the first common lines during the early radiation of angiosperms, possibly reflecting adaptation to more open habitats. Phylogenetic analyses clarify the position of Cretaceous mesofossils in molecular trees of Recent taxa. Plants that produced Asteropollis pollen, with tepals adnate to a single carpel, are nested in crown group Chloranthaceae with Hedyosmum; Canrightiopsis, with three stamens and no perianth, is sister to Sarcandra and Chloranthus; and Canrightia is a stem relative that illustrates a still bisexual stage in floral reduction. Plants that produced Pennipollis pollen are related to Chloranthaceae and/or Ceratophyllum rather than monocots. Appomattoxia, which produced Tucanopollis pollen, has equivocal affinities, but Pseudoasterophyllites, with similar pollen and stems with reduced leaves, may be a link between Chloranthaceae and Ceratophyllum. These results imply that flowers became unisexual before losing the perianth, while bisexual flowers in Canrightiopsis, Sarcandra, and Chloranthus are secondarily derived from unisexual flowers.     

Aeropalynological study of two selected locations in North-Central Nigeria

Pollen and spores have been found as major biological sources of morbidity among individuals sensitive to respiratory disorders. The aim of the present study was to analyse the deposition rate of atmospheric pollen and fern spores at selected sites in Benue and Plateau states of the North-Central Nigeria between July 2015 and June 2016. This was accomplished by: (1) determining the pollen and fern spore content of each monitoring station; (2) establishing the relationship between total pollen count and meteorological parameters; and (3) comparing the recovered airborne pollen spectra with identified plants in the surrounding vegetation types of the sampling sites. The collection of atmospheric pollen was done using a modified Tauber sampler and plants in the surrounding environment of the sampling sites were enumerated. The residual solution was collected monthly and acetolysed, after which slide preparation and microscopy of the treated residue were done. Meteorological data were obtained from the Nigerian Meteorological Agency, Lagos. The results obtained reveal seasonal distribution patterns of various airborne pollen grains in the study locations. The most abundant pollen types recovered in Plateau State were produced by Syzygium guineense, Tridax procumbens, Alchornea sp., Terminalia sp., Poaceae and Amaranthaceae. Pollen types of Casuarina equisetifolia, Syzygium guineense, Tridax procumbens, Poaceae and Cyperaceae were preponderant in Benue State. Pteris sp., Nephrolepis sp. and a trilete fern spore were also represented in this study. The recovered airborne pollen spectra correspond favourably with some identified plants in the study locations. There was no significant correlation between monthly total pollen count and mean monthly values of meteorological parameters in Benue State. Air temperature and wind speed correlated significantly with monthly total pollen count in Plateau State. It is suggested that the allergenic effect of these abundant pollen types on humans should be further examined.     

Modern pollen assemblages from human-influenced vegetation in northwestern China and their relationship with vegetation and climate

Modern pollen spectra can improve the interpretation of fossil pollen records used to reconstruct past vegetation, climate and human impacts. It is important, therefore, to carefully examine the relationships between modern pollen spectra, vegetation, climate and human activity. Here, we present the results of an analysis of the pollen spectra of 143 surface pollen samples from farmland, wasteland, desert, steppe/meadow, forest and river valley along a transect from Lanzhou to Urumqi, in northwestern China. The modern pollen assemblages are mainly composed of Amaranthaceae, Artemisia, Poaceae, Asteraceae, Ephedra and Nitraria. The results indicate that in general the surface pollen assemblages of different vegetation types reliably represent the modern vegetation in terms of the composition of the main taxa and the dominant types. Farmland is dominated by cereal-type (≥?15%) and Amaranthaceae (≥?20%), while the pollen assemblages of wasteland (i.e. the vegetation immediately surrounding farmland) are mainly composed of Amaranthaceae (≥?25%), Artemisia (≥?20%), Poaceae (≥?10%), Asteraceae (≥?5%) and Cyperaceae (≥?5%). Amaranthaceae (≥?45%) and Ephedra (≥?10%) are the most important taxa in desert, and Cyperaceae (≥?35%) and Thalictrum (≥?2%) are the dominant pollen types in steppe/meadow. Forest and river valley samples are characterized by high frequencies of Picea (≥?10%) and Cyperaceae (≥?20%). Both constrained and partial canonical ordination techniques (RDA and partial RDA) of the main pollen types and environmental variables show that the modern pollen spectra are primarily controlled by mean annual precipitation (MAP). Cyperaceae, Thalictrum and Brassicaceae are positively correlated with MAP and negatively correlated with mean July temperature (T_July), while the representation of certain other types, such as Amaranthaceae, Ephedra and Nitraria, is negatively correlated with MAP and positively correlated with T_July. The Human Influence Index (HII) is significantly correlated with cereal-type pollen, and it can also differentiate human-influenced and natural vegetation. Our results provide a basis for improving the interpretation of fossil pollen records from arid northwestern China and similar regions.